1. Field of the Invention
The present invention relates to a colored microlens array for focusing incident light at a plurality of positions by a predetermined color arrangement such as Bayer arrangement and a manufacturing method for the colored microlens array. In particular, the present invention relates to a colored microlens array for a colored microlens and an inner-layer lens used for a color solid-state image capturing apparatus consisting of semiconductor elements for performing photoelectric conversions on and capturing image light from a subject, used for a color liquid crystal display apparatus, and a manufacturing method for the colored microlens array; a color solid-state image capturing device using the colored microlens array and a manufacturing method for the color solid-state image capturing device; a color display apparatus such as a color liquid crystal display apparatus using the colored microlens array and a manufacturing method for the color display apparatus; and an electronic information device, such as a digital camera (e.g., digital video camera and digital still camera), an image input camera, a scanner, a facsimile machine and a camera-equipped cell phone device, having the color solid-state image capturing device as an image input device used in an image capturing section of the electronic information device.
2. Description of the Related Art
In recent years, a color solid-state image capturing device using a semiconductor element (e.g., CCD (Charge Coupled Device) image sensor, CMOS (Complementary Metal Oxide Semiconductor) image sensor) is used variously as an electronic information device of a finished product, such as a digital camera, a video camera, a camera-equipped cell phone device, a scanner, a digital copying machine, and a fax machine. With the spread of the color solid-state image capturing device, the demand for not only high-functioning and high-performance, such as more number of pixels and more light receiving sensitivity, but also downsizing and lower pricing are increasing still more.
With the advancement of downsizing and more number of pixels (more pixels and more dense pixels) for the color solid-state image capturing device as well as the demand for lower pricing, the size of the pixel installed in the color solid-state image capturing device becomes even smaller. With such a reduction of the pixel, the light receiving sensitivity decreases, which is one of the fundamental performances of the color solid-state image capturing device. As a result, a clear image capturing of a subject will be difficult in a place with low luminous intensity. Therefore, it is important how to increase the light receiving sensitivity per unit pixel.
As a method for increasing the sensitivity of the color solid-state image capturing device, techniques, such as forming a microlens, which is composed of an organic high molecule material, on a color filter (Reference 1, for example), and further forming a lens under a color filter and inside a laminated structure between a light receiving section and the color filter for positioning a so-called inner-layer lens (Reference 2, for example), are known.
Such a microlens and inner-layer lens increase the light focusing rate for incident light entering vertically onto the light receiving section, thereby increasing the sensitivity of a solid-state image capturing element (light receiving section). However, the focal point comes off the center of the light receiving section for incident light entering obliquely, which has a non-vertical incident angle. In particular, the amount of light decreases in a peripheral section of the light receiving section, causing poor image quality. This phenomenon becomes more noticeable as the distance increases between the microlens and the light receiving section, relatively with the miniaturization of the pixel.
Therefore, what is required as a function of the color solid-state image capturing device with more downsizing and more impacted pixels, is a way to improve the light receiving sensitivity by the microlens and the inner-layer lens, and at the same time, a way to maintain a short distance between the microlens and the light receiving section described above. As such a technique, Reference 3 proposes a forming method for a colored microlens array on a CCD. The forming method for the colored microlens array will be described with reference to FIG. 8.
First, a light receiving section 102, a CCD charge transfer channel 104, and a channel stopper 105 are respectively formed on a surface of a semiconductor substrate 101, as illustrated in FIG. 8(a). The light receiving section 102 performs photoelectric conversions on and captures image light from a subject, functioning as a photoelectric conversion section. The CCD charge transfer channel 104 reads out a signal charge from the light receiving section 102 through a readout section 103 so as to consecutively transfer the signal charge in a predetermined direction. The channel stopper 105 separates the periphery of one element including the light receiving section 102 and the CCD charge transfer channel 104. Further, a charge transfer electrode 107 is formed above the CCD transfer channel 102 with an insulation film 106 interposed therebetween. Further, an interlayer insulation film 108 is formed on the charge transfer electrode 107, and a shielding film 109 is formed in such a manner to avoid covering the light receiving section 102.
Subsequently, a first planarizing film 110, such as BPSG (Boro-Phospho-Silicate Glass), is layered on the insulation film 106 and the light shielding film 109 as illustrated in FIG. 8(b). The surface is smoothed by a second planarizing film 111 as illustrated in FIG. 8(c). Subsequently, a color filter array 112 is formed by a pigment dispersed resist or dye method on the second planarizing film 111 as illustrated in FIG. 9(d), the color filter array 112 having a blue color filter 112B, a green color filter 112G, and a red color filter 112R coupled in a mosaic and arranged by the Bayer arrangement. Subsequently, a microlens shape pattern 113, which is a transfer resist pattern, is formed to be positioned above the corresponding light receiving section 102 functioning as a photoelectric conversion section as illustrated in FIG. 9(e), the microlens shape pattern 113 formed in a lens shape similar to a convex-shaped microlens shape using an organic high molecule material.
Using the microlens shape pattern 113 as a mask, respective color filters 112B, 112G and 112R are etched simultaneously by anisotropy etching such as RIE (Reactive Ion Etching), so that color filters 112B, 112G and 112R are formed in such a manner to be copied in respective convex-shaped lenses, as illustrated in FIG. 9(f). As a result, a colored microlens array is formed, the colored microlens array composed of colored microlenses 114B, 114G and 114R that are colored in each color and positioned above corresponding light receiving sections 102 functioning as a photoelectric conversion section.
Reference 1: Japanese Publication for Opposition No. 2945440
Reference 2: Japanese Laid-Open Publication No. 11-40787
Reference 3: Japanese Laid-Open Publication No. 5-206429